High-frequency cavity resonator apparatus



Dec. 13, 1949 1 F. SORG HIGH-FREQUENCY CAVITY RESNATOR APPARATUS 2 Sheets-Sheet l Filed Jan. 20, 1945 Y .il Lm mail INVENTOR BfL/O/YO ESORG A7/ ATTORNEY Dec. 13, 1949 L. F. soRG HIGH-FREQUENCY CAVITY RESONATOR APPARATUS 2 Sheets-Sheet 2 Filed Jan. 2o, 1945 |NVENTOR y0 550k@ BY W7 TTORNEY Illillllilllll vlllilllllti Patented Dec. 13, 1949 HlGHfFREQUENCY CA vrry RESONATOR APPARATUS Lloyd F, Sorg, Garden City, N. Y., assgnor to The Sperry Corporation,l a corporation of Delaware Application January 20, 1945, Serial No. 573,734

19 Claims.

The present invention relates, generally, to high frequency tube'structures having enclosed oscillatory circuits. ofthe type disclosed in Patent No. 2,242,275 issued May 20, 1941, in the name of Russell H. Varian, andthe invention has reference, more particularly, tonovel improvements in .thisstypeof structure operating at frequencies of the. order et 1,0* eveles ner: seeond. and in methods or fabricating. eheh. structuren 'the invention in another oi ite, aaneets` 1feletes. to nevel. features. of the instrumentalities and methods deeoribed herein for achieving the principal objects of the invention and to the novel principles. employed inthose instiumentalities and methods; whether-or. not these features and prinoinleeare used for the said principal objeete or in the same eld or art.l

Theprinoinal. obieet oi this. invention is to provide a high frequency tube structure having hole low resonators. provided with concentric line terminals having energy transfer means extend- 111g. in tq the interior of said resonators for selectively removing energy therefrom or delivering energy thereto., said concentricV line terminals being adapted to have concentric lines removably attached vthereto foreiecting use of this tube structure as an oscillator, amplifier, detector, etc., as desired.

Another object of this invention is to provide a novel tube structure wherein various metal components of the tube may be assembled and sealed together, on a mass production basis, while glassbearing components of the tube are separately fabricated as subassembles, said subaSSembleS, thereafter, being inserted and sealed in the assembled tube. by the. application of loealiaed heat thereby minimizing the danger of injury to said glass-hearing components. during such sealing operations.

further object of the present invention is to provide a novel tube structure having a concentric line terminal wherein means are provided` for controlling the positioning of energy transfer means inthe resonator during construction there- .by minimizing the danser of over.- or under-coupling between the resonator and eXternai circuits employed therewith.

Still. another obieet ef the invention lies in the provisiones? a novell eoneentrie line terminal. strncture designed generally to simplify tube manufacture and to prevent injury to the'line terminal.

' Still another object of thev present invention is to provide a method of manufacturing high freque'noy tn bes having a novel concentric line terminal strnoture which makes it possible to manufacture such a structure in extremely small size and, at the same time, economically, efciently and with minimum ei'ort.

A featnre of the invention lies in the relativelydshdort coaxial line structure which is herein prov1 e Another feature of this invention lies in the provision of a novel concentric line terminal structure having a glass bead seal between 'an inner conductor and an outer conductor, saidseal being adapted to connect the inner and outer conductors as a preformed subassembly which may thereafter be inserted in a terminal post provided on the wall of the resonator and sealed thereto, at a point remote from the glass-.to-.metal seal, thereby minimizing the danger or straining or fracturing said seal.

Still another feature of the invention is to provinde a novel coaxial line terminal device having a hollow terminal post and a preformed coaxial line terminal assembly and positioning means associated therewith which serve to hold theY assembly in proper alignment with respect to surrounding parts when 'the assembly. is inserted? inf'the post duringV manufacture.

A further object of the invention is to provide improved apparatus, instrumentalities, and rnevethodsV embodying novel features and principles, adapted for use in realizing the above objects,l and also adapted for use in other elds. i

The above and other objects. and advantages of my invention will be apparent from the particular deseription thereof` made in connection with the accompanying drawings in which.:

Figi.. 1 is. a view in eide eiealatioh, partly in seetien, of the novel tube struetuie of the present invention;

Fie- 2 is. an enlarged, irasihentarv, sectional view showing, a complete ooneentrio line terminal structure;

Fien, 3 to 5,. inclusivel are seetienai views. of everal modified forms of concentric line strucures;

Fig. 6 is an exploded view, partly in elevation and partly in longitudinal section, of an assembling device for the concentric line terminalsho'wn inFigs.2orl; Y

Fig. 'l is a longitudinal sectional view of an assembling device illustrating an additional Astep in the process of making the terminal unit shown inFlg.2; and

Fig. o shows a completed concentric lin e terminal unit subassembly.

Similar reference characters are used in al1 of the above figures to indicate corresponding parts.

Referring now to the drawing, and particularly Fig. 1 thereof, a novel tube structure is shown as comprising a pair of spaced, cylindrical, evacuated, concentric shells I9, l2, having opposed resilient inner end Walls I4, I6 that are centrally apertured and secured on a drift tube I5. The drift tube I5 has its end portions projecting into the interiors of shells Ill, I2 which end portions terminate adjacent, though somewhat spaced from, rigid, transverse partitions 2S, 28. The ends of the drift tube I5 are provided with grid structures II, l 9 which may be of the type disclosed in Figs. 8 or 9 of Letters Patent No. 2,345,642, issued April 4, 1944, in the names of Sigurdv F. Varian and Russell H. Varian, or of any other suitable type.

A second pair of grids I8, 20, similar to grids I'I, I9 are contained in aligned central apertures provided for this purpose in the partitions 26, 28. The grids Il, I9 and I8, 29 and the axis of the driit tube I5 are preferably coaxial with each other and with the axis of the shells I9, I2. The wall l 4 and the partition 26 together with the cylindrical side wall 42 of the shell I0 and the projecting end of the drift tube I5 define a hollow resonatorv Ill. A similar hollow resonator I2' is dei-ined Within the shell l2, said resonators being adapted to contain standing electromagnetic waves.

A suitably mounted cathode or electron gun assembly 32 is aligned with the resonator grids for projecting a beam of electrons therethrough. A collector electrode 35 connected to an external lead 35 is likewise suitably mounted in the tube for collecting electrons traversing the tube.

For the purpose of coupling'the resonators Ill and I2 to external circuits in ultra high frequency fashion,v novel loop and coaxial line structures 34, 35 are provided. The structures 34, 36 communicate with the interior of the resonators Ill, I2 through threaded openings 3B,V 40 which are formed radially in side walls 42, 43 respectively. Inasmuch as the coaxial line structures employed are of similar construction, a full description of either one, say the structure 34, may be taken as descriptive of the other.

. As illustrated in Fig. 2 the coaxial line structure 34 comprises a Vsubstantially cylindrical post member 39 containing a coaxial line terminal l unit or subassembly, generally designated by the numeral 56, said unit including an outer conductor or shell 69 and an inner conductor or lead 52 concentrically supported in said outer conductor by a glass bead seal 64 formed therein, v. in a manner` hereinafter to be described in detail.

The post 39 is preferably shaped to provide a portion 44 having a uniform, relatively large diameter and a portion 46 of uniform, relatively reduced diameter with a tapered shoulder por- 4,

tion 4a intermediate and joining said uniform portions 44, 46. The post 39 is rigidly and vacuum sealed to the resonator i9' by inserting the relatively reduced portion 46 thereof in the threaded opening 3B, and welding or brazing the post 3a over the opening 38.

Y The coaxial line terminal unit 58, in accordance with the teaching of the present invention, is a prefabricated subassembly adapted to be snugly received by and sealed into the post 39. the outer conductor 69 is preferably formed to provide enlarged and reduced portions 65 and 68 respectively, with a tapered intermediate portion lli, in a manner similar and conformable to the said portions 44, 46 and 48 of the post 39. The

Hence, l

tapered portion 48 acts as a stop or motion-limiting means which, by its coaction with the tapered portion la, serves to limit the inward movement of the terminal unit 58 when said unit is inserted in the post 3S. In this manner, I can properly position the terminal unit 58 relative to the resonator I9'.

As hereinbefore described, the inner conductor 62 is concentrically supported in the outer conductor 6U by the glass bead or other insulating seal 54. It will be observed that the location of the seal 64 coincides with the tapered portions 48, 'I3 thus attributing to said portions the added function of centering the inner conductor 32 relative to the outer conductor 69. The inner conductor E2 extends into the resonator I0' in the form of a coupling loop 'I2 of any desired shape and in accordance with one of the features of the present invention, the extent to which the loop projects into the resonator, is determined by the above-described motion-limiting means. Hence, the uncertainty commonly involved in the type and degree of coupling which may be eifected between the resonator and an external circuit is denitely minimized. Y

As illustrated in the embodiment of Fig. 2, the loop is substantially J-shaped with the bight portion thereof smaller than the internal diameter of the reduced portion 4B of the post 39. The outer end of the loop 'I2 is spot-welded or silver-soldered to the inner surface of the outer conductor 59. It will be observed further, that the inner conductor 62 comprises a pair of concentric wires 62', 62" of unequal diameters axially joined end to end, as by butt-welding or any other suitable method. The portion 62 of larger diameter forms part of the glass-metal seal, hence is preferably made of Kovar, or similar fusible metal or alloy, while the portion 62" of smaller diameter, of which the loop l2 is fashioned, is preferably of Dumet, a copper-coated iron wire, selected for ease in welding to said Kovar portion 62. It will be understood that the use of any metal or alloy having the desired properties of Kovar, on the one hand, and Dumet, on the other, is entirely within the scope ofthe present invention.

The ratio of the diameters of the Kovar portion 52' and the Dumet portion 52, respectively, are selected so that the ratio of the internal diameter of the outer conductor E9 to the outside diameter of the inner conductor 62 is substantially constant throughout the entire length of the coaxial line terminal unit 53. In this manner, any electrical discontinuity, introduced by the tapered portions and the uniform portions of unequal diameters, is effectively nulliiied.

To minimize the danger of injuring the glassto-metal seal by bending forces or torques experienced by the inner conductor 62 during normal handling, I provide a weakened portion 14 in said inner conductor to permit the conductor to bend thereat and thereby absorb the force or torque which might otherwise be transmitted, with injurious results to the seal. As a precaution against injury or breaking of the inner conductor 62, the latter is preferably disposed within the outer conductor 69 so that the outer end of said inner conductor 52 terminates interiorly of the outer end of the outer conductor 69. Thus the innerv conductor B2 is completely shielded from mechanical forces by the side walls of both the outer conductor 69 and the post 39.

;.-After insertion in the post 39,'ithe. coaxialterminal Lunitfffis rigidly and permanently secured 'thereto, and vacuum sea1ed,.as by brazingswelding, orfthe `lile,.at a region 16 adjacent-the outer ends ofthe terminal unit 58 and post-'39,respeotively, and spaced from the glass beadvsealfil. It will, thus, be observed that thepossibility rof injury of the glass bead seal, due to vheat and pressure accompanying the brazing operation, is

substantially reduced.

Connection between the coaxial line structure 34 and an external circuit is made bymeans of a. coaxial transmission line 59 having an internally threaded coupling memberv5i2 adapted to be Vreceived on a threaded boss v54providedfor the purpose on the enlarged portion 44 of Vthe post 39. The transmissionline 5!) further comprises atubular outer conductor 5l and an inner `conductor 53 of which at least the end portion is hollow, vas indicated at 55. In coupling the transmission line v5) to the coaxial line terminall structure 34, the line 59 is slipped over the structure 34 so that the inner conductor 62 is snugly tted into the hollow portion of the `inner conductor 53 and the outer conductor 5l slides over the post 39. Satisfactory electrical contact is insured by tightening the coupling member 52 A`over the boss 54.

Amodied coaxial terminal structure, adapted for use with a couplingvloop whose'bight portion is large compared to the opening provided by the reduced portion 48 of the post 39, vis shown in Eig. 3. As shown, a uniform, cylindricaljhol- Vlow terminal `post 18 is provided with an indentation or dimpleV 8E! in a side wall, said inden- W tation forming in the interior of the post'18 an embossment or detent 83. The indentation A80 -is preferably formed by means of a punch orvsimilar tool, -hitwith a blow of known magnitude so that the depth of said indentation is'predetermined and controlled.

The exact location of the indentation Y8) and, hence, that of the detent 83, is set with refervencetothe wall 42 ,of the resonator |0,-such that, when the terminal unit 58 is inserted in `.the post, the outer portion of the Shoulder 19 engages the detent 83 and the innerend of the shell 80 lies flush with the inner end of the post 18 and the wall 42. Clearly, the detent 83 .and

the shoulder 10 coact to provide stop or motiony limiting means which serve kto positionthe assembly 58 relative to the post 18 and the resonator-Ill. It will be noted, however, that in assembling the prefabricated assembly/58 land the post 18, said assembly is inserted into the post 18 with the plane of its enlarged loop 92 an- `and kept uniform, corresponding to the position of detent 83.

A modified form of coaxial line terminal unit 84 is illustrated in Fig. 4, and is here shown employed with the type of terminal post 18 shown' in Fig. 3. Asubstantially uniform, thin walled, cylindrical outer conductor or shell 85 is shown having a relatively narrowand shallow circular groove or channel 88 peripheraliy rolled or-other- VWise vformed. therein, said -groove or channel `tent 83 in the post -18.

forming, in the .interior ofsaid outer conductor fan-,inwardly projecting embossment .88 ata position corresponding to the position of the de- The embossment 88-coacts `withthe detent 83 to provide stop -or mo- `rtion-limiting'means which serves-to position the terminal unit 83 relative to the -post 18 and the resonator I8'. It will be observed that the em- :bossment also serves-as means tending to positiona preformed glass bead during the process ofVY making the .coaxial line terminal unit 84, kas

`Willhereinafter be described. In assembling said terminal unit 84 and the post 18, the unit is sprung or snapped into position and firmly and tpositively retained therein by the seatingof the detent-63111 the groove 86.

Thereafter, unit 84 maybe sealedto post 18 at its upper edge, re-

Vmote from seal 98, in `a fashion similar to the -device of Figs.f2 and `3.

In the'event that the outer conductor .85 is .fabricated with thick-walled, relatively inflexible,

vtubular stockfsuch that the process of springing or snapping the unit 84 into position is undesirable, a modified post structure, shown in Fig. 5 may be usedin lieu of the post 'i3 of Fig. 4. A straightsided, cylindrical post member 92, having a threaded -end inwardly tapered or turned to Aform a neck 94, is inserted in the threaded opening 38 of the resonator I9 so that said neck 94 `extends slightly beyond the inner surface Vof the -wallf42 and into the resonator I9'. Theneck 94 vformsastop or motion limiting means for .prop- 'erly-positioning the coaxial line terminal unit 84 relative to the post 92 'and the resonator I0. yIf .desired,neck= 94 need not protrude into resona- `tor I8', but may terminate ush with the inner i surface of Wall 42.

There hereinbefore described structure not lonly incorporates-novel and improved structural featuresv but also has been particularly designed for fabrication by novel mass production methods. In particular, the coaxial line terminal units 58 (Fig. 2) and '84 (Fig. 4) are both espevcially 'adapted for such production methods and ya preferred method is described below with reference to Figs. 6 throughS wherein the construction of' unit 58, taken as an example, is illustrated' in detail.

The inner conductor or shell which also may lbe ofKovar or an equivalent Yglass-bonding metal, 'is preliminarily prepared for glassing rst, by :.'sandblasting the interior surface thereof and, then, by preoxidizing it in an air oven at a tern- `perature of about i758 F. for a period of approximately three minutes. This preliminary treatment, it has been found, renders the metallic suryface more readily fusible to glass.

Similar preparatory' operations are performed on the inner `conductor 82 for the same reason.

V-Inassembling before sealing, `the inner con- -ductor-SZ is supported in a jig E98 which comiprises an elongated cylindrical member i il! whose upper end is terminated in transversely extendingcollarfi 88 which, in turn, supports a cylindrical stud i109 coaxially aligned with collar its and cylindricalfmember tei. The Acomponents of the jig 'itt are suitably joined to Aform a rigid structure having van axial bore 82 extending theretliroughadapted to receive the unlooped small diameter portion Si?" and to support the larger diameter nortion 5?. of the inner conductor 62 in 'l a substantially vertical position, by virtue of .the

wshoulder.formed at the joint of portions 82 and 82", *slipped/over .the upstanding.portion 82 of -tlie as illustrated in Fig. The shelled is vinner conductor 62 and is supported in a vertical position, concentric with the inner conductor 62,

.the enlarged portion of the inner conductor 62. A type of glass having a desirable thermal coefficient of expansion relative to that of Kovar is produced by and available from the Corning Glass Works and is identified by the type number loll, although any material forming a vacuum-tight seal with conductors 55.1 and 52 may be used. One end of the bead it is champfered as at llt, to conform with the tapered shoulder lil of shell 60. The bead is also provided with a longitudinal bore H2 whose diameter is slightly greater than the diameter of the portion 52 of the inner conductor 52, so that the latter may freely be passed through the bore H2. The outside diameter of the bead is somewhat less than the inside diameter of the shell 6l] to admit the bead It freely into the shell Sii, to be positioned therein by shoulder 'le cooperating with champferl l lil. A refractory cap lili may oe placed over the assembled shell, inner conductor and bead whereby the inner conductor 62 is centered and held rmly in position during the subsequent heating operation.

As shown in Fig. '7, the jig It@ and the assembled elements are then placed in radio frequency induction furnace' H6 of which a concentrator ring HB is directed toward that portion of the assembly containing the bead iil and the metal surfaces to be fused thereto. Heat generated by the furnace llt is thus uniformly applied to the glass and the metal surfaces adjacent to the glass under time-temperature controlled conditions. It will be observed that heat is substantially uni.- formly distributed throughout the glass bead, since induction takes place at both the shell-glass surface and the inner conductor-glass surface, resulting in a satisfactory, vacuum tight seal.

After the seal has been made, the terminal unit 53 may be removed from the jig and annealed in I..

an air furnace to relieve any strains that may exist in the glass. After the annealing process has been completed the smaller portion t2 may be formed into a loop 'l2 of any desired size and shape, with the outer end of the loop spot-welded or silver-soldered to the inner surface of the outer conductor tt. If desired, the end portion of the wire S2 may be ilattened, as at lZu, in press before forming the loop, to facilitate forming the loop in desired shape and size.

As shown in Fig. 2, the coaxial line structure 311 is assembled by inserting the terminal unit 53 into the hollow post 39 on the tube, until the tapered shoulder portion 'l is seated firmly in the tapered shoulder portion 48 and the loop 'l2 is correctly positioned in the resonator it. When so seated, it will be noted, that the outer end of conductor Gt terminates interiorly of the outer end of post 39 to provide an annular ledge or projection lil on which a ring 22 or brazing material such as,

silver-solder or the like may be placed.

Time-temperature controlled localized heat to seal the conductor 653 to post 3 is applied to the region 1B adjacent the outer ends of conductor post 39 and ring 22 in the presence of a Yhydrogen atmosphere which serves to prevent the formation of undesirable oxides, the presence of which in an evacuated tube, is known to interfere with satisfactory exhaustion of the tube. A metal-to-metal, Vacuum-tight seal between the 'terminal unit'58 and the post 39 is thus effected with Virtually no harmful effect on the glass-tometal seal E4. In view of the fact that the heat employed for the metal-to-rnetal seal is localized and electively isolated from the glass-metal seal, I can substantially reduce the over-all length of the coaxial line structure Sli with respect to prior known structures of this type.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. High frequency apparatus comprising means defining a hollow resonator chamber adapted to contain an electromagnetic field, a hollow terminal post carried directly by said resonator having an opening affording access to said chamber, limiting means in said post, and means providing electrical coupling to said field from externally of said chamber comprising means conductive to high frequency energy at the inner surface of said post, and extending therealong a substantial distance predetermined by said limiting means, said conductive means being insertable within said post through the opening in said post, and means vacuum sealing said opening.

2. .A high frequency structure comprising a hollow resonator adapted to contain an electromagnetic eld, a hollow terminal post carried directly by said resonator and communicating with the interior thereof, means in said post for arresting the movement of a body inserted in said post, and a concentric line terminal unit within said terminal post comprising an outer conducting shell and an inner conducting lead, means on said outer shell engaging said arresting means to position said terminal unit in said post, said lead extending inwardly beyond the inner end of said shell and into said hollow resonator to provide coupling with the eld within said resonator said outer shell lining at least a substantial portion of the inner surface of said post.

'3. High frequency apparatus comprising a hollow resonator, a hollow terminal post carried directly by said resonator, a concentric line terminal within said terminal post comprising an outer conducting shell lining at least a substantial portion of the inner surface of said post and an inner conducting lead, said lead extending inwardly beyond the inner end of the shell and into the hollow resonator to provide coupling with the field within said resonator, and means on said post cooperable with further means on said shell for limiting the degree of extension of said lead within the resonator.

4. The apparatus claimed in claim 3 in which said means comprises a tapered shoulder portion in said post and said further means comprises a conformably-shaped shoulder portion on said shell.

5. The apparatus claimed in claim 3 wherein said means comprises a detent formed at a predetermined portion of said post and said further means comprises a tapered shoulder in said shell.

6. The apparatus claimed in claim 3 wherein said means comprises a first embossment in said vpost comprisingan-outer conducting post and said further `mea-ns comprises a second yembossment in said shell.

:7. The apparatusfclaimed in claim 3 wherein said means comprisesa neck formed in the end of said post and lsaid -further means comprises an adjacent endvof said-shell in abutment with said neck.

8. High frequency apparatus comprising a hollow resonator, a lhollow concentric line terminal post carried by said resonator, at -ieast vL a portion of said post having 'tapered side walls, -a concentric line terminal within said terminal shell having -a #corresponding portion thereof tapered in conformityfwith the tapered walls of said post and an inner Aconducting lead, said lead terminating short of the outer Vend of said sheil and ex- -tending inwardly inthe form voi a loop beyond the inner end of the shell and into the vhollow resonator, #the penetration of said loop in said resonator being .fixed by the coaction between the taper of said post and the taper of said terminal, said loop having its` doubled-over end connected to the inner surface of said shell, and .-a vacuum seal between the inner porion of said shell and said lead.

9. lHigh frequency vacuumtube apparatus comprising -a hollow resonator, va hollow terminal 4postcarried directly-byfsaid'resonator and communicating Awith the interior thereof, means in Lsaid post denning'a-stop, electrically conductive .means comprising-a coaxial line section unit dislposed in part interior-ly of said post and in part -interiorly of said resonator, said conductive means 'having means cooperative.with said stop for deltei-mining the .degree oi insertion of vsaid Vconductive means .in said resonator, and means vacuum sealing said conductive means to said post at a region remote from said resonator, said coaxial line section unit extending along a substantial portion of the inner surface of said post.

10. High frequency apparatus comprising a hollow resonator, a tubular terminal post vacuumsealed thereto at an aperture in the wall of said resonator and communicating with the interior thereof, positioning means on said post, a concentric line coupling within said terminal post, comprising an outer conducting shell having means cooperable with said positioning means for disposing said shell within said terminal post so that the inner end of said shell lies flush with the wall of said resonator, and an inner conducting lead vacuum-sealed to said outer conducting shell and con ected therewith by a loop beyond the end of said shell and within said hollow resonator.

1l. A coaxial line terminal device for coupling to electrical wave energy fields comprising a central conductor having an end loop, a hollow terminal post having a relatively constricted portion, said post being disposed around said conductor and having an open end toward said loop with the loop outside the terminal post, electrically conductive means at the inner surface of said terminal post having a constricted portion adapted to seat on said constricted portion of said terminal post to be positioned thereby, and an electrical connection between the end of said loop and said conductive means.

l2. A coaxial line terminal device for coupling to the electrical wave energy fields Within an evacuated high frequency resonator device, comprising a central conductor, a hollow terminal post supported by said high frequency device and concentric with and spaced outside said conductor, means forming a partial obstruction in said the tapered section of said lterminal post,.andfan electrically conductive liningmember within said terminal post, said lining member being adapted to be positioned in said terminal-postlby said partial obstruction, and a loop on said conductor contacting said lining Amember anddisposed in the evacuated space of said device.

i3. Aconcentric line terminal device as in claim i12, y'further comprising means at one end of said lpost -vacuurn sealing said terminal post to said resonator land .further means at the other end Ioiisaidpost.vacuumsealing said post to said lining member.

le. High frequency-electron discharge tube ap- .paratuscomprising.means dening a hollow resonator chamber adapted to contain an electromagnetic-field, means `for projecting a beam of yelectrons :through said resonator in energy exehangingrelation therewith, a hollow post carried directly-by said resonator Vhaving an opening afifording access to :said chamber, means in said post restricting the size of the opening, means providing lfixed velectrical coupling to said iield ffromfoutsidefsaid ychamber comprising a section of coaxial transmission `line disposed within said post-andextending along the inner surface of said post at least a'substantial distance predetermined `by said restricting means, means vacuously seal- `ing saidpost tosaid line section, and means vacuum sealing saidopening at a point remote from saidresonator.

l5. A fhigh frequency structure comprising a .hollow resonator adapted to contain an electro- .magneticfiielda tubular terminal post carried by :said resonator and communicating with the interior thereof, vmotion arresting means within said -post,.and.a coaxial coupling unit within said post, .said coupling unit comprising an outer conductor lining at least a substantial portion of the inner surface of said post, said outer conductor being at one end flush to the wall of said resonator, an inner conductor concentrically disposed in said outer conductor, means providing a vacuum seal within said outer and inner conductors, means sealing said outer conductor to said post at the end thereof remote from said resonator, and means on said outer conductor engaging said motion arresting means for positioning said coupling unit within said post, said inner conductor extending beyond said vacuum-sealing means and into said hollow resonator whereby coupling with the eld is provided.

16. A high frequency coupling device for a cavity resonator, comprising a hollow post adapted to communicate directly with the interior of said resonator; a coaxial coupling unit within said post comprising an outer conductor having two portions of dierent inner diameter joined by a tapered section, the larger-diameter portion of said outer conductor extending along the inner surface or said hollow post, an inner conductor coaxially within said outer conductor, and a glass bead vacuum sealed to both said conductors and having a tapered section sealed to outer conductor, said inner conductor having an end extending beyond the free end of the smaller-diameter portion of said outer conductor and beyond said post and connected to the free end of said outer conductor smaller-diameter portion to form a loop; said post having a detent therein engaging the tapered section of said outer conductor, the extent of said outer conductor along the inner surface of said post being predetermined by the engagement of said detent and said tapered section; and

-hermetical-sealing means joining said post and vouter conductor, and a glass bead sealed to both said conductors; a loop connected to the end of said inner conductor within the smaller-diameter `portion of said outer conductor and extending beyond said portion of said outer conductor, said loop also being connected to said outer conductor at its smaller-diameter portion; said post having a detent engaging the tapered section of said outerconductor, and said outer conductor eX- tending along the inner surface of said post a distance predetermined by the engagement of said detent and said tapered section; and a hermetical-sealing means joining said post and said outer conductor larger-diameter portion at their ends remote from said loop.

18. AV Vhigh frequency lcoupling device for a cavity resonator, comprising a hollow post adapted to communicate directly with the interior of the resonator; a coaxial coupling unit within said post comprising an outer conductor having two portions of different diameter joined by a tapered section, an inner conductor within said outer conductor, and a glass bead sealed to both said conductors; a loop connected to the end of said inner conductor Within the smaller diameter portion of said outer conductor and extending beyond said portion of said outer conductor, said loop also being connected to said outer conductor at its smaller diameter portion; said post having a detent engaging the tapered section of said outer conductor, and said outer conductor extending along the inner surface of said post a distance predetermined by the engagement of said detent and said tapered section.

19. A high frequency coupling device for a cavity resonator, comprising a hollow post adapted to communicate directly with the interior of the resonator; a coaxial coupling unit within said post comprising an outer conductor having two portions of different diameter joined by a tapered section, a loop-terminated inner conductor within said outer conductor, and a glass bead sealed to both said conductors at said tapered section; said post having a detent engaging the tapered section of said outer conductor, and means sealing said outer conductor to said post at the ends thereof remote from said loop.

' LLOYD F. SORG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,490,845 December 13, 1949 LLOYD F. SORG It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 33, for electrode 35 read electrode S8; column 4, line 13, for the reference numeral 73 read 70; column 6, line 38, for the Word There read The and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the oase in the Patent Office.

Signed and sealed this 16th day of May, A. D. 1950.

[SML] THOMAS F. MURPHY,

Assistant 0ommz'szoner of Patents.

Certificate of Correction Patent No. 2,490,845 December 13, 1949 LLOYD F. SORG It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 38, for electrode 35 reed electrode 33; column 4, line 18, for the reference numeral 7 3 read 70; column 6, line 88, for the Word There read The and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the ease in the Patent Office.

Signed and sealed this 16th day of May, A. D. 1950.

THOMAS F. MURPHY,

Assz'stant Uommz'sgz'aner of Patents. 

